Shape critical properties of patterned Permalloy thin films

Abstract

The effects of shape and edges in magnetic elements with reduced dimensions on the magnetization reversal of cross- and framed cross-shaped Ni79Fe21 (30nm) films were studied. Remagnetization details in the stripes of the patterned structures, which had 3 μm to 30 μm widths and ~100 μm lengths, were visualized by the magneto-optical indicator film technique. The magneto-optic images revealed three different types of the domain structure formation and evolution in the samples during their magnetization reversal: (i) spin rotation with growth and annihilation of a cross-tie structure in the stripes perpendicular to the applied field, (ii) nucleation and fast motion of special boundaries, which consist of a number of coupled vortices located along both edges of the stripes parallel to the applied field, and (iii) nonuniform magnetization rotation with macrodomain nucleation and domain wall motion in the large unpatterned part of the films. It was experimentally revealed that there exists a dependence of the critical field for nucleation and motion of domain walls in the parallel-to-field stripes on their width and frame width. In particular, an inverse proportionality between this nucleation field and stripe width was found. Both experimental and simulation results show that, in cases (i) and (ii), the magnetostatic fields, which are formed on the edges of the stripes and at their intersections, play a crucial role in the formation of spin inhomogeneities and switching of the samples.

Domain wall induced modulation of low field H-T phase diagram in patterned superconductor-ferromagnet stripes

“…2(a) and 2(b) are taken for field values near the coercive field. As we reduce the field from positive saturation, the domain nucleation starts from the edges of the stripe to minimize the demagnetization energy 34 . The domain reversal happens in a similar way in both the images, however, the domain wall region is more pronounced in the panel (b) (Bloch regime) compared to panel (a) (Néel regime).…”

Ferromagnetic Resonance Studies in Magnetic Nanosystems

“…The exchange stiffness constant for Py is of the order of A ex = 1.3 × 10 −11 J•m −1 [35], which allows us to evaluate the spin wave constant D = 2A ex /M s . Using a value of M s = 0.7 T (from fits of the in-plane VNA-FMR data of the 10 nm thick Py reference sample), we obtain D = 4.309 × 10 −17 T•m 2 .…”

Adjusting microwave sensing frequency through aspect ratio variation and bending repetitions in Permalloy ellipses

“…Adjusting the dimensions of magnetic elements to influence shape anisotropy plays a pivotal role in meticulously fine tuning coercivity, bolstering magnetic stability, and steering the magnetization dynamics. These adjustments are indispensable in the engineering and design of radio frequency (RF) absorbing devices, as they have a profound impact on the performance of these devices [28][29][30][31]. Moreover, the magnetomechanical effect, which is closely related to stress anisotropy, stands as a cornerstone for deciphering how resonance frequency is influenced by the direction of applied stress and the frequency of bending repetitions in flexible magnetic thin films and patterns [36][37].…”